Battery module, and rechargeable battery for constituting the battery module

ABSTRACT

A battery module is provided which includes multiple rechargeable batteries coupled together. The battery module includes multiple prismatic cell cases having short lateral walls and long lateral walls arranged side by side. Adjacent short lateral walls are integral with each other. The battery module includes holes extending through the short lateral walls of the cell cases at upper edge portions. The battery module also includes a pair of frame fittings that have base ends and protruding portions in each of the cell cases for connecting two adjacent cell cases. The protruding portions of the pair of frame fittings extend into the through holes in the upper edge portions of the short lateral walls of the cell cases from both sides and are welded together. Positive and negative electrode collector plates in the cell cases are respectively attached to the base ends of the frame fittings. End frame fittings that have base ends and protruding portions for cell cases are located at both outer ends of the rechargeable battery for connecting the cell cases to outside terminals. Connection terminals that have protruding portions are connected to the end frame fittings at both outer ends of the rechargeable battery.

The present application is a divisional of pending U.S. patentapplication Ser. No. 09/614,769, filed Jul. 12, 2000, entitled “BatteryModule, and Rechargeable Battery for Constituting the Battery Module”,the disclosure of which is expressly incorporated herein by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery module, and in particular toa rechargeable battery for constituting the battery module in which theinternal battery resistance can be made small and the battery output canbe increased.

2. Description of Related Art

FIG. 10 shows a conventional battery module made by connecting aplurality of rechargeable batteries and coupling them together as one soas to obtain the necessary power. In this battery module, a plurality ofcells 41 (41 a to 41 j) made of sealed alkaline rechargeable batteriesas shown in FIG. 11 are arranged side by side, with the long lateralwalls of the battery cases 42 adjacent each other. End plates 52 arearranged against the outside of the cells 41 a and 41 j at both ends,and the two end plates 52 and 52 are bound together with binding bands53 so as to couple the cells together as one piece.

For the cells 41, an electrode plate group 47, comprising positiveelectrode plates and negative electrode plates layered with interveningseparators, thus constituting elements for electromotive force, isaccommodated in a battery case 42 together with a liquid electrolyte,and the open end of the battery case 42 is closed with a lid 46 providedwith a safety vent 45. From the upper end at one side of the positiveelectrode plates forming the electrode plate group 47, leads 49 extendupward and are connected to a positive electrode terminal 43 above them,and similarly, from the upper end of the other side of the negativeelectrode plates, leads 49 extend upward and are connected to annegative electrode terminal 44 above them. The positive electrodeterminal 43 and the negative electrode terminal 44 are attached to thelid 46.

The positive electrode terminals 43 and negative electrode terminals 44of coupled neighboring cells 41 are connected by connection plates 51,thereby connecting all cells 41 in series. When the battery cases 42 arecoupled, ribs 48, which protrude vertically from the long lateral wallsof the battery cases 42, are abutted against each other, forming coolantpassages running in the vertical direction along the long lateral wallsof the battery cases 42 in the space between ribs 48. The cells 41 a to41 j are cooled by flowing air through these coolant passages.

However, with the configuration for the cells 41 of this conventionalbattery module, leads 49 extend from a portion at the upper end on oneside of the electrodes and are connected to the electrode terminals 43and 44, and consequently, there were the problems that the internalresistance of the battery was large, because the average distance fromthe surface of the electrodes to the collector portions of the leads 49was long, and that the power output was low, because the utilizationrate of the electrode active material was low.

Moreover, because the terminals 43 and 44 protruding to the outside ofthe lid 46 are connected by connection plates 51, it is necessary toprovide space for this connection at the upper end of the battery cases42. Furthermore, since the connection portions are exposed, there is theproblem that the space for installing this battery module cannot be madecompact.

Moreover, in the portions where electrode pillars of the electrodeterminals 43 and 44 extend through the lid 46, O-rings for providing aseal are usually placed only on the inner side of the lid 46, and therewas the danger that electrolyte may leak during use of the battery.

SUMMARY OF THE INVENTION

In view of these problems of the prior art, it is an object of thepresent invention to provide a rechargeable battery, of which internalbattery resistance is small and of which battery output can be improved.A further object of the present invention is to provide a batterymodule, of which installation space can be made, and in which there isno danger of electrolyte leakage.

To achieve the above object, the present invention provides arechargeable battery, comprising:

a prismatic cell case having short lateral walls and long lateral walls;and

a group of electrodes accommodated inside the cell case, the group ofelectrodes including a plurality of positive and negative electrodeplates arranged alternately and substantially in parallel to the longlateral walls of the cell case with an intervening separatortherebetween;

wherein lateral edges of the positive electrode plates protrude beyondthe negative electrode plates on one side, and lateral edges of thenegative electrode plates protrude beyond the group of positiveelectrode plates on the opposite side, the protruding portions forminglead portions.

Since the lateral portions on one side of the electrode plates serve aslead portions, the average distance from the surfaces of the electrodeplates to the collector portions can be made short, the internal batteryresistance can be made small, and the utilization rate of the electrodeactive material becomes large, whereby the power output of the batterycan be increased.

The lateral edge portions of the negative electrode plate and positiveelectrode plate lead portions of the group of electrodes are attached torespective collector plates, and the group of electrodes is thus held bythe collector plates. Therefore, the group of electrodes can be heldwith a compact configuration, and the surface area of the regions forgenerating an electromotive force can be made large, whereby the batterycapacity can be increased.

The collector plates are provided with curved portions at both endsthereof for clamping the group of electrodes. Thereby, the electrodes donot spread and extend toward the outside of the collector plates whenthe group of electrodes are attached to the collector plates, and theelectrodes can be fixed reliably to the collector plates.

By setting D<L ≦4D, where L is the length of a side of the lead portionsof the electrodes and D is the length of a side in a directionperpendicular thereto, the average distance from the surfaces of theelectrode plates to the collector portions can be made even shorter, andthe above-noted effects can be enhanced. If D≧L, the ratio of the spacefor connecting the cells, that is formed between the upper edge of theelectrode plate group and the upper wall of the cell case, against thevolume of the electrode plate groups becomes large. As the proportion ofthe dead space increases, the battery capacity is compromisedaccordingly, but this problem can be solved when L and D are set asnoted above. On the other hand, if L>4D, the aspect ratio(vertical/horizontal) becomes too large, which leads to problems withregard to other structural conditions, such as maintaining the strengthof the collector plates or manufacturing of the cell cases. Moreover, ifL>4D, there is the problem that temperature variations are large betweenthe two ends of the electrode plate groups in the flow direction of thecoolant when the outer walls of the cell case are cooled by letting acoolant flow in the longitudinal direction along the lead portions ofthe electrode plate groups, but this problem does not occur when L and Dare set as noted above.

In the cell case in which a group of electrodes is accommodated, whichis made of electrode plates whose dimensions are set to D<L≦4D as notedabove, by setting d<l<4d, where l is the length of the long lateralwalls of the cell case in the direction parallel to the lead portions ofthe electrodes, and d is the width of the long lateral walls in thedirection perpendicular thereto, the proportion of the dead space isoptimized and the battery capacity is increased. Moreover, thetemperature variations between the upper portion and the lower portionof the electrode plates can be reduced, when the cell case is cooled byletting the coolant flow in the vertical direction of the long lateralwalls of the cell cases.

As mentioned above, the lateral edge portions of the group of positiveelectrode plates protrude beyond the group of negative electrode plateson one side, and the lateral edge portions of the group of negativeelectrode plates protrude beyond the group of positive electrode plateson the opposite side form the lead portions. Therefore, a single,belt-like separator can be arranged in a zigzag fashion between thepositive electrode plates and the negative electrode plates. In thisway, the separator can be arranged easier between the electrode platesthan by covering the electrode plates with bag-shaped separators.

The rechargeable battery according to the present invention can beconstructed such that:

a plurality of cell cases are coupled together as one piece with theshort lateral walls of the cell cases being mutually integrated, therebyconstituting an integral battery case;

upper open ends of the cell cases are closed by an integral lid member;and

the collector plates in adjacent cell cases are connected to each othervia a connection fitting that extends through the short lateral wallsbetween the adjacent cell cases.

Thereby, the neighboring cells can be connected to each other inside theintegral battery case, and the space for setting up the rechargeablebattery can be made compact.

Furthermore, through holes are formed in the short lateral walls betweentwo adjacent cell cases at an edge portion; and the connection fittingcomprises a pair of frame fittings, each frame fitting having a base endand a protruding portion that is inserted into the through holes, thedistal ends of the protruding portions being welded together, and thecollector plates being attached to the base ends of the frame fittings.Thereby, the collector plates can be connected easily by welding with apair of frame fittings.

According to the present invention, a battery module can be constitutedby coupling a plurality of rechargeable batteries together, each of therechargeable batteries, accommodating therein a group of electrodes anda liquid electrolyte, wherein:

a plurality of prismatic cell cases having short lateral walls and longlateral walls are arranged side by side, with adjacent short lateralwalls being integral with each other;

the group of electrodes inside a cell case including a positiveelectrode collector plate and a negative electrode collector platearranged at lateral opposite ends of the cell case in the direction ofthe long lateral walls thereof;

through holes are formed in the short lateral walls of the cell cases atupper edge portions thereof;

a pair of frame fittings comprising base ends and protruding portionsare provided for each of the cell cases for connecting two adjacent cellcases, the protruding portions of the pair of frame fittings beinginserted into the through holes formed in the upper edge portions of theshort lateral walls of the cell cases from both sides and weldedtogether, and the positive and negative electrode collector plates inthe cell cases being respectively attached to the base ends of the framefittings;

end frame fittings having base ends and protruding portions are providedfor cell cases located at both outer ends of the rechargeable batteryfor connecting the cell cases at both outer ends of the rechargeablebattery to outside terminals; and

connection terminals having protruding portions are connected to the endframe fittings of the cell cases at both outer ends of the rechargeablebattery.

Thereby, the connection between the cell cases and the outside of thecell cases can be carried out easily with a compact configuration.

Moreover, a sealing material is provided around the protruding portionsof the frame fittings and the connection terminals, so as to provide aseal between the two adjacent cell cases, whereby both sides of theconnection configuration can be sealed double, and leakage of liquidelectrolyte during use of the battery can be prevented.

While novel features of the invention are set forth in the preceding,the invention, both as to organization and content, can be furtherunderstood and appreciated, along with other objects and featuresthereof, from the following detailed description and examples when takenin conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a battery module according toone embodiment of the present invention;

FIG. 2 is a partial vertical lateral cross-sectional view of the same;

FIG. 3 is a cross-sectional view taken in the direction of the arrowsalong the line III—III in FIG. 2;

FIG. 4 is a front view of an electrode plate group of the sameembodiment;

FIG. 5 is a cross-sectional view taken in the direction of the arrowsalong the line V—V in FIG. 4;

FIG. 6A is a front view,

FIG. 6B is a top plan view, and

FIG. 6C is an enlargement of VIC in FIG. 6B, showing the positiveelectrode plate in the same embodiment;

FIG. 7A is a front view,

FIG. 7B is a top plan view, and

FIG. 7C is an enlargement of VIC in FIG. 7B, showing the negativeelectrode plate in the same embodiment;

FIG. 8 is a vertical cross-sectional view showing the configuration of aportion connecting two cells in the same embodiment;

FIG. 9 is an exploded perspective view of an electrode plate group inanother embodiment of the present invention;

FIG. 10 is an external perspective view of a conventional batterymodule; and

FIG. 11 is a partially cutaway perspective view of a cell of the sameconventional example.

DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of a battery module according to the presentinvention will be hereinafter described with reference to FIGS. 1 to 8.

The battery module of this embodiment is a nickel metal hydride battery,which is suitable for use as a drive power source for an electricvehicle. As shown in FIGS. 1 to 3, the battery module 1 is made up of aplurality of (six in the example shown in the drawing) cells 6, arrangedin a row. Cell cases 3 of each of the cells 6, which are formed in aprismatic fashion with short lateral walls, long lateral walls, and opentop ends, are mutually integrated on their short lateral walls, therebyconstituting an integral battery case 2. The upper open ends of the cellcases 3 are closed all together by an integral lid member 4.

Each of the battery cases 3 constitutes a cell 6, accommodating thereinelectrode plate groups 5 together with electrolyte. An electrode plategroup 5 comprises a large number of positive electrode plates andnegative electrode plates arranged parallel to the long lateral walls ofthe cell cases 3 and layered in the direction of the short lateral wallsof the cell cases 3, with intervening separators therebetween. Theconstruction inside the battery case will be described later in moredetail.

Connection holes 7 are formed at the upper edge portions of the outershort lateral walls of the cell cases 3 at the two ends of the integralbattery case 2 and between each two cell cases 3. Positive and negativeconnection terminals 8 are respectively mounted to the connection holes7 at the outer short lateral walls of the two outer cell cases 3, andconnection fittings 9 for serially connecting two adjacent cells 6 aremounted to the connection holes 7 in the intermediate short lateralwalls between each two cell cases 3. In addition, the lid member 4 isprovided with one safety vent 10 for each of the cell case 3, so as torelease pressure when the internal pressure in the cell cases 3 hasexceeded a certain value. Moreover, a sensor mounting hole 11 formounting a temperature detection sensor for detecting the temperature ofthe cells 6 is formed at suitable cells 6 or for each cell 6.

The long lateral walls of six cells 6 together form an integral sidewall 12 of the integral battery case 2. On this side wall 12 of theintegral battery case 2, protruding ribs 13 that extend vertically areprovided at positions corresponding to the lateral edges of two adjacentcell cases 3. Further, a large number of relatively small circularprotrusions 14 are formed at suitable intervals in matrix fashionbetween each two ribs 13. The ribs 13 and the protrusions 14 have thesame height. Furthermore, coupling ribs 15 a and 15 b having the sameheight as the ribs 13 and the protrusions 14 are formed on the sidewalls of the upper edge of the cell cases 3 and the side walls of thelid member 4, such as to bridge across the side walls of the cell cases3 and the lid member 4, at positions corresponding to an extension ofthe ribs 13 and the protrusions 14. A plurality of protrusions 16 andindentations 17, for positioning and fitting together integral batterycases 2 when their side walls 12 are abutted on each other, are arrangedat an upper portion and a lower portion of the outer surface of the tworibs 13 near both ends of the side wall 12 of the integral battery case2. When a plurality of integral battery cases 2 are arranged in a row inparallel to constitute a battery module, the ribs 13, the protrusions 14and the coupling ribs 15 a and 15 b form coolant passages for coolingthe cell cases 3 effectively and uniformly.

The aforementioned electrode plate groups 5 are explained in detail withreference to FIGS. 4 to 7. In FIGS. 4 and 5, a plurality of positiveelectrode plates 18 and negative electrode plates 19 are arrangedalternately, and the positive electrode plates 18 are covered withseparators 20 in the form of a bag having an opening on one side. Thepositive plates 18 and the negative plates 19 are stacked upon oneanother with separators 20 therebetween, thereby constituting theelectrode plate group 5. In FIG. 4, the region where the positiveelectrode plates 18 and the negative electrode plates 19 oppose eachother with the intervening separators 20 and generate electric power isindicated by oblique lines. The lateral edges of the group of positiveelectrode plates 18 protrude beyond the group of negative electrodeplates 19 on one side, and the lateral edges of the group of negativeelectrode plates 19 protrude beyond the group of positive electrodeplates 18 on the opposite side, and these protruding lateral portionsform the lead portions 18 a and 19 a, to the lateral ends of whichcollector plates 21 and 22 are welded, respectively. The outer edges ofthe collector plates 21 and 22 are bent toward the inside as shown inFIG. 5, in order to restrict the dimensions of the electrode plates 18,19. The collector plates 21, 22 are welded to the electrode plates 18,19, so that the, electrode plates 18, 19 do not spread outwards aspressure is applied thereto. Numeral 23 denotes external separatorsarranged at the outer faces of the electrode plate group 5 between thecollector plates 21 and 22.

The positive electrode plates 18 are made of Ni foamed metal. As shownin FIGS. 6A-6C, the lead portion 18 a is constructed by compressing onelateral edge of the plate of foamed metal and attaching a lead plate 24on one surface of the lead portion 18 a by ultrasonic welding or seamwelding. The negative electrode plates 19 shown in FIG. 7 are made of Nipunched metal coated with an active material except for lead portions 19a. “L” denotes the length of a side of the positive electrode plate 18and the negative electrode plate 19 where the lead portions 18 a and 19a are provided, and “D” denotes the length of the side in a directionperpendicular thereto. The positive and negative electrode plates 18, 19are configured so that “L” is larger than “D”, but not larger than fourtimes “D”.

Numeral 29 denotes pairs of positioning holes formed in the leadportions 18 a and 19 a at a suitable distance from the top and thebottom thereof. By inserting positioning pins into these positioningholes 29 and by applying pressure on the lateral ends of the leadportions 18 a and 19 a, these lateral ends of the lead portions 18 a and19 a are aligned and welded reliably and evenly to the collector plates21 and 22.

FIG. 8 shows the connection fitting 9 for serially connecting the cells6. The connection fitting 9 comprises a pair of frame fittings 25, tothe base ends of which the upper ends of the collector plates 21 and 22of two neighboring cells 6 are welded, respectively. The cells 6 areconnected by inserting from both sides protruding portions 26 projectingfrom an axial portion of the frame fittings 25 into the connection hole7 formed in the short lateral walls of the cell cases 3, and abuttingtheir leading faces against each other and welding them together. Thebonding of the upper ends of the collector plates 21 and 22 to the baseends of the frame fittings 25 and the welding of the leading faces ofthe protruding portions 26 are performed by resistance welding alltogether after they have been assembled. Annular grooves 27 are formedaround the protruding portions 26 of the frame fittings 25, and theconnection hole 7 is sealed double with O-rings 28 mounted in theseannular grooves 27.

In the battery module 1 of the present invention, as described above,the integral battery case 2 is constituted by mutually connecting aplurality of prismatic cell cases 3, abutted on their short side walls.The open ends of the cell cases 3 are closed by the integrated lidmember 4, and the collector plates 21, 22 of the electrode plate groups5 in adjacent cells 6 are connected via the connection fittings 9, thatpass through the connection holes 7 formed in the upper edges of theshort side walls of each cell case 3. Therefore, neighboring cells 6 canbe connected inside the integral battery case 2. Since the connectionconfiguration is not exposed to the outside, the installation space forthe battery module 1 can be made compact.

The connection fittings 9 are made of pairs of frame fittings 25 havingprotruding portions 26, which are inserted into the connection holes 7from both sides and whose leading ends are welded together, and to whosebase ends the collector plates 21 and 22 are attached, so that theelectrode plate groups 5, i.e., the cells 6 of neighboring cell cases 3can easily be connected in series by welding the frame fittings 25.Also, by arranging connection terminals 8 having similar protrudingportions 26 and frame fittings 25 on the outer short lateral walls ofthe two cell cases 3 at opposite ends and by welding the leading ends oftheir protruding portions 26, 26 together, the connection of the cellcases 3 on either end with an external terminal can be performed with acompact configuration and in a simple manner.

Moreover, thanks to the O-rings 28 for sealing the cell cases 3 providedaround the protruding portions 26 of the frame fittings 25 and theconnection terminals 8, both sides of the short lateral walls ofadjacent cell cases 3 are sealed double and leakage of liquid during usecan be prevented reliably.

In the electrode plate groups 5 of the cells 6, the lateral edgeportions of the group of positive electrode plates 18 protrude beyondthe group of negative electrode plates 19 on one side, and the lateraledge portions of the group of negative electrode plates 19 protrudebeyond the group of positive electrode plates 18 on the opposite side,and these protruding lateral portions form the lead portions 18 a and 19a, to which collector plates 21 and 22 are welded over their entirelength. Therefore, the average distance from the surfaces of theelectrodes 18 and 19 to the collector plates 21 and 22 can be madeshort, and as a result, the internal battery resistance can be madesmall and the utilization rate of the electrode active material becomeslarge, which increases the battery output. In FIG. 4, the collectorplates 21 and 22 are attached to the lead portions 18 a and 19 a overtheir entire length, but substantially the same effect can be attainedif the collector plates 21 and 22 are attached to the lead portions 18 aand 19 a over at least half the length of the lead portions 18 a and 19a.

Moreover, the groups of electrode plates 18 and 19 are held in a simpleconstruction by attaching the lateral edge portions of the lead portions18 a and 19 a of the electrode plates 18 and 19 to the collector plates21 and 22, whereby the surface area of the regions for generating anelectromotive force becomes large, and the battery capacity can beincreased.

The length L of a side of the electrode plates 18, 19 where the leadportions 18 a, 19 a are provided, and the length D of the sideorthogonal to L are set D<L≦4D, so that the average distance from theentire surfaces of the electrode plates to the collector plates can bemade even shorter. If D≧L, the ratio of the space for connecting thecells 6, that is formed between the upper ends of the electrode plategroups 5 and the upper wall of the lid member 4 (dead space), againstthe volume of the electrode plate groups 5 (space where electromotiveforce is generated) becomes large. As the dead space increases, thebattery capacity is compromised accordingly, but this problem can besolved with the above-described configuration.

On the other hand, if L>4D, the aspect ratio (vertical/horizontal)becomes too large, which leads to the problem with regard to otherstructural conditions, such as maintaining the strength of the collectorplates 21 and 22 or manufacture of the cell cases 3. Furthermore, ifL>4D, large temperature variations would occur between the lower end andthe upper end of the electrode plate groups 5, when a plurality ofintegral battery cases 2 are arranged side by side and their outer wallsare cooled by flowing a coolant in the vertical direction perpendicularto the direction in which the cell cases 3 are arranged, that is, in thelongitudinal direction along the lead portions of the electrode plategroups 5. Such problem can be prevented by setting “L” and “D” are setas described above.

Moreover, if the length l of the long lateral walls of cell cases 3parallel to the lead portions 18 a, 19 a of the electrode plates 18, 19and the length d of the short lateral walls of the cell cases 3 asindicated in FIG. 2 are set d<l≦4d, the proportion of the abovementioned dead space can be optimized and the battery capacity can beincreased. Also, the temperature variation between the upper end and thelower end of the electrode plates can be reduced, when the cell cases 3are cooled by letting the coolant flow in the vertical direction of thelong lateral walls of the cell cases 3.

Next, another embodiment of a rechargeable battery in accordance withthe present invention will be described with reference to the FIG. 9. Inthe aforementioned embodiment, the positive electrode plates 18 arecovered by bag-shaped separators 20, so that the separators 20 areprovided between the positive electrode plates 18 and the negativeelectrode plates 19. Since the lateral edge portions of the group ofpositive electrode plates 18 protrude beyond the group of negativeelectrode plates 19 on one side, and the lateral edge portions of thegroup of negative electrode plates 19 protrude beyond the group ofpositive electrode plates 18 on the opposite side, and these protrudinglateral edge portions form the lead portions 18 a and 19 a, theseparator can be arranged in a zigzag fashion between the positiveelectrode plates 18 and the negative electrode plates 19 as shown inFIG. 9. This embodiment employs such meandering arrangement of theseparator 30. In this way, the separator can be arranged easier betweenthe electrode plates 18 and 19 than by covering each of the electrodeplates with the bag-shaped separators 20.

As has been explained above, in the rechargeable battery in accordancewith the present invention, the lateral edge portions of the group ofpositive electrode plates protrude beyond the group of negativeelectrode plates on one side, and the lateral edge portions of the groupof negative electrode plates protrude beyond the group of positiveelectrode plates on the opposite side, and these protruding lateral edgeportions form the lead portions. Thus one lateral edge of each electrodeplate serves as a lead portion, and thereby the average distance fromthe surfaces of the electrodes to the collector portions can be madeshort. Accordingly, the internal battery resistance can be made smalland the utilization rate of the electrode active material becomes large,whereby the power output of the battery is increased.

Although the present invention has been fully described in connectionwith the preferred embodiment thereof, it is to be noted that variouschanges and modifications apparent to those skilled in the art are to beunderstood as included within the scope of the present invention asdefined by the appended claims unless they depart therefrom.

What is claimed is:
 1. A battery module with a plurality of rechargeablebatteries coupled together, each of the rechargeable batteriesconfigured for accommodating therein a liquid electrolyte and a group ofelectrodes comprising a group of positive electrode plates and a groupof negative electrode plates, the battery module comprising: a pluralityof prismatic cell cases having short lateral walls and long lateralwalls arranged side by side with adjacent short lateral walls beingintegral with each other, and upper open ends of the plurality ofprismatic cell cases being integrally closed with a single lid member;the group of electrodes inside a cell case including a positiveelectrode collector plate and a negative electrode collector platearranged at laterally opposite ends of each of the group of positiveelectrode plates and the group of negative electrode platesrespectively; holes extending through the short lateral walls of thecell cases at upper edge portions thereof; a pair of frame fittingscomprising base ends and protruding portions in each of the cell casesfor connecting two adjacent cell cases, the protruding portions of thepair of frame fittings extending into the through holes in the upperedge portions of the short lateral walls of the cell cases from bothsides and being welded together, and the positive and negative electrodecollector plates in the cell cases being respectively attached to thebase ends of the frame fittings; end frame fittings having base ends andprotruding portions for cell cases located at both outer ends of therechargeable battery for connecting the cell cases at both outer ends ofthe rechargeable battery to outside terminals; and connection terminalshaving protruding portions connected to the end frame fittings of thecell cases at both outer ends of the rechargeable battery.
 2. Thebattery module of claim 1, further comprising a sealing material aroundthe protruding portions of the frame fittings and the connectionterminals, so as to provide a seal between the two adjacent cell cases.